The present invention relates to a single-substrate-processing CVD (Chemical Vapor Deposition) apparatus and method, and particularly to an apparatus and method for growing an insulating, high-dielectric, or ferroelectric film by means of MOCVD (Metal Organic Chemical Vapor Deposition).
In order to manufacture semiconductor devices, film formation and pattern etching are repeatedly applied to a semiconductor wafer. As semiconductor devices are increasingly highly miniaturized and integrated, demands on the film formation become more strict. For example, very thin insulating films, such as capacitor insulating films and gate insulating films are still required to be thinner and to be more insulating.
Conventionally, silicon oxide films and silicon nitride films are used as the insulating films. In recent years, however, it has been proposed to form the insulating films from materials having more excellent insulating properties, such as metal oxides, e.g., tantalum oxide (Ta2O5), or high-dielectric or ferroelectric bodies containing two metal elements or more, e.g., (Ba,Sr)TiO3, i.e., BST. These films can be formed by means of MOCVD, i.e., using vaporized metal organic compounds.
When a film is formed by means of CVD, it is important to maintain a high planar uniformity in the film thickness, in light of attaining a high yield and the like. For this reason, process gases are supplied from gas spouting holes arranged at uniformly distributed positions on a shower head, so that the process gases are uniformly supplied onto the surface of a wafer. Where a CVD process is performed to form a film of a two-element material including only one metal or semiconductor element, represented by SiO2 or TiN, it is possible to maintain a high planar uniformity in the film thickness by such a shower head.
According to experiments conducted by the present inventors, however, where a CVD process is performed to form a film of a composite material including two metal elements or more, such as a BST thin film, planer uniformity in the film composition is sometimes lowered by this conventional CVD process. Like planar uniformity in the film thickness, planar uniformity in the film composition, i.e., the ratio of metal elements, is also an important issue, in light of attaining a high yield and maintaining electric properties.
Further, where a tantalum oxide film is formed by means of MOCVD, a raw material gas containing tantalum alkoxide, and oxygen gas are used. In this case, reaction byproducts, such as organic substances, e.g., CH3CHO, are slightly mixed into the tantalum oxide film, thereby deteriorating the film""s properties, such as the insulation breakdown voltage.
An object of the present invention is to provide a single-substrate-processing CVD apparatus and method which can improve planar uniformity in film composition, where a film of a composite material including two metal elements or more is formed.
Another object of the present invention is to provide a single-substrate-processing CVD apparatus and method which can reduce the amount of reaction byproducts contained in a film to be formed by means of CVD.
According to a first aspect of the present invention, there is provided a single-substrate-processing CVD apparatus for forming a thin film containing first and second metal elements on a target substrate while supplying first and second process gases containing the first and second metal elements, respectively, a precursor of the first metal element produced by dissociation of the first process gas having a lower activation energy and a higher resistivity than a precursor of the second metal element produced by dissociation of the second process gas, the apparatus comprising:
an airtight process chamber;
a worktable arranged in the process chamber to mount the target substrate thereon;
an exhaust system configured to exhaust the process chamber; and
a supply system having a shower head configured to supply the first and second process gases into the process chamber, wherein the shower head has a shower region facing the worktable, on which a group of first spouting holes for spouting the first process gas and a group of second spouting holes for spouting the second process gas are arranged, and wherein the supply system is designed such that the first process gas is supplied at a spouting rate substantially uniform over the shower region, and the second process gas is supplied at a spouting rate gradually decreasing in radial directions outward from a center of the shower region.
According to a second aspect of the present invention, there is provided a single-substrate-processing CVD method of forming a thin film containing first and second metal elements on a target substrate while supplying first and second process gases containing the first and second metal elements, respectively, a precursor of the first metal element produced by dissociation of the first process gas having a lower activation energy and a higher resistivity than a precursor of the second metal element produced by dissociation of the second process gas, the method comprising:
placing the target substrate on a worktable arranged in an airtight process chamber; and
forming the thin film on the target substrate by supplying the first and second process gases into the process chamber from a shower region facing the worktable while exhausting the process chamber, wherein the first process gas is supplied at a spouting rate substantially uniform over the shower region, and the second process gas is supplied at a spouting rate gradually decreasing in radial directions outward from a center of the shower region.
According to a third aspect of the present invention, there is provided a single-substrate-processing CVD apparatus for forming a thin film containing a metal element on a target substrate while supplying first and second process gases containing the metal element and a non-metal element for combining with the metal element, respectively, the apparatus comprising:
an airtight process chamber;
a worktable arranged in the process chamber to mount the target substrate thereon;
an exhaust system configured to exhaust the process chamber; and
a supply system having a shower head configured to supply the first and second process gases into the process chamber, wherein the shower head has a shower region facing the worktable, on which a group of first spouting holes for spouting the first process gas and a group of second spouting holes for spouting the second process gas are arranged, and wherein the group of the first spouting holes are arranged to distribute in a first zone having a surface area substantially smaller than a surface area of the target substrate facing the shower region, and the group of the second spouting holes are arranged to distribute in a second zone concentric with the first zone and having a surface area substantially the same as or larger than the surface area of the target substrate.
According to a fourth aspect of the present invention, there is provided a single-substrate-processing CVD method of forming a thin film containing a metal element on a target substrate while supplying first and second process gases containing the metal element and a non-metal element for combining with the metal element, respectively, the method comprising:
placing the target substrate on a worktable arranged in an airtight process chamber; and
forming the thin film on the target substrate by supplying the first and second process gases into the process chamber from a shower region facing the worktable while exhausting the process chamber, wherein the first process gas is supplied from a first zone having a surface area substantially smaller than a surface area of the target substrate facing the shower region such that the first process gas is supplied at a spouting speed higher than a spouting speed at which the first process gas would be supplied from a zone having the same surface area as the surface area of the target substrate when an equal supply rate is used, and the second process gas is supplied from a second zone concentric with the first zone and having a surface area substantially the same as or larger than the surface area of the target substrate.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.